In aircraft maintenance it is necessary, on a frequent and systematic basis, to drain the fuel from the tanks or sumps of the aircraft.
Among the reasons for this maintenance procedure is to prevent the growth of micro-organisms in the tanks. Such micro-organisms, if allowed to establish themselves in the tanks, can cause serious corrosion problems, can obstruct filters, and can alter the characteristics of the fuel quantity transmitter located in the tank, which can cause false fuel quantity readings on the gauges in the cockpit. This, of course, can cause very severe consequences indeed, including the possibility of crashing the aircraft.
During such maintenance procedures, it is necessary that the maintenance personnel visually inspect the fuel as it is being drained to look for contaminants, micro-organisms, and the like. Further, it is important, from the point of view of economy and quickly "turning around" the aircraft so that it can continue in commercial use, that the maintenance procedures be performed as quickly as possible.
In addition, it is necessary that the sump drainage procedures be done as safely as possible as to not exposing the personnel doing the work to being splashed or the like by the jet fuel which they are handling.